Polyurethane foams are widely known and used in automotive, housing and other industries. Such foams are produced by reaction of a polyisocyanate with a polyol in the presence of various additives. One such additive is a chlorofluorocarbon (CFC) blowing agent which vaporizes as a result of the reaction exotherm, causing the polymerizing mass to form a foam. The discovery that CFCs deplete ozone in the stratosphere has resulted in mandates diminishing CFC use. Production of water-blown foams, in which blowing is performed with CO2 generated by the reaction of water with the polyisocyanate, has therefore become increasingly important. Tertiary amine catalysts are typically used to accelerate blowing (reaction of water with isocyanate to generate CO2) and gelling (reaction of polyol with isocyanate).
The ability of the tertiary amine catalyst to selectively promote either blowing or gelling is an important consideration in selecting a catalyst for the production of a particular polyurethane foam. If a catalyst promotes the blowing reaction to a too high degree, much of the CO2 will be evolved before sufficient reaction of isocyanate with polyol has occurred, and the CO2 will bubble out of the formulation, resulting in collapse of the foam. A foam of poor quality will be produced. In contrast, if a catalyst too strongly promotes the gelling reaction, a substantial portion of the CO2 will be evolved after a significant degree of polymerization has occurred. Again, a poor quality foam, this time characterized by high density, broken or poorly defined cells, or other undesirable features, will be produced.
Tertiary amines also influence other foam physical properties including air flow, hardness, tensile, tear, compression set and load loss, as well as changes to those physical properties in response to humid ageing. There remains a need in the industry for additives allowing the systematic variation of specific physical properties. Tertiary amine compositions frequently contain diluents, particularly diols such as ethylene glycol, butanediol and dipropylene glycol. The diols serve to dissolve solid tertiary amines and adjust composition viscosity for convenient handling. The diols are not thought to contribute significantly to foam physical properties at typical use levels. Mono-alcohols are not typically used as diluents since mono-functional reactants are chain terminators. Chain termination weakens the polymer network and degrades physical properties.
U.S. Pat. No. 5,770,674 discloses a RIM method for making gaskets from a specific polyurethane/urea composition that includes a low molecular weight chain extender selected from the group consisting of polyols, primary amines, secondary amines, amino alcohols and their mixtures and shows 2-methyl-1,3-propanediol.
U.S. Pat. No. 6,506,810 discloses the use of mixtures of branched alcohols including 2-ethyl-1-hexanol and organofunctionally modified polysiloxanes in the production of flexible polyurethane foams.
U.S. Pat. No. 6,780,895 discloses components of a polyurethane carpet backing and tuft bind adhesive requiring low or ultra low unsaturation polyoxypropylene polyols and 2-methyl-1,3-propanediol as a chain extender.
U.S. Pat. No. 6,872,758 discloses the optional use of 2-methyl-1,3-propanediol as a chain extender in thermoformable polyurethane foam with excellent low temperature compression set resistance.
WO 00/55232 discloses the optional use of chain extenders including dipropylene glycol and 2-methyl-1,3-propanediol as ingredients in foam compositions designed to improve ease of removal from molds.